Thomas Hobbes (15881679). Of Man, Being the First Part of Leviathan.The Harvard Classics. 190914.

Chapter V

Of Reason and Science

WHEN a man reasoneth he does nothing else but conceive a sum total, from addition of parcels, or conceive a remainder, from subtraction of one sum from another; which, if it be done by words, is conceiving of the consequence of the names of all the parts, to the name of the whole; or from the names of the whole and one part, to the name of the other part. And, though in some things, as in numbers, besides adding and subtracting men name other operations, as multiplying and dividing, yet they are the same; for multiplication is but adding together of things equal; and division but subtracting of one thing, as often as we can. These operations are not incident to numbers only, but to all manner of things that can be added together, and taken one out of another. For as arithmeticians teach to add and subtract in numbers, so the geometricians teach the same in lines, figures, solid and superficial, angles, proportions, times, degrees of swiftness, force, power and the like; the logicians teach the same in consequences of words, adding together two names to make an affirmation, and two affirmations to make a syllogism; and many syllogisms to make a demonstration; and from the sum, or conclusion, of a syllogism they subtract one proposition to find the other. Writers of politics add together pactions to find mens duties, and lawyers laws and facts, to find what is right and wrong in the actions of private men. In sum, in what matter soever there is place for addition and subtraction there also is place for reason, and where these have no place, there reason has nothing at all to do.

Out of all which we may define, that is to say determine, what that is which is meant by this word reason, when we reckon it amongst the faculties of the mind. For reason in this sense is nothing but reckoning, that is adding and subtracting, of the consequences of general names agreed upon for the marking and signifying of our thoughts; I say marking them when we reckon by ourselves, and signifying when we demonstrate or approve our reckonings to other men.

And, as in arithmetic, unpractised men must, and professors themselves may often, err, and cast up false; so also in any other subject of reasoning the ablest, most attentive, and most practised men may deceive themselves, and infer false conclusions; not but that reason itself is always right reason, as well as arithmetic is a certain and infallible art; but no one mans reason, nor the reason of any one number of men, makes the certainty; no more than an account is therefore well cast up, because a great many men have unanimously approved it. And therefore, as when there is a controversy in an account the parties must by their own accord set up for right reason the reason of some arbitrator, or judge, to whose sentence they will both stand, or their controversy must either come to blows, or be undecided, for want of a right reason constituted by Nature; so is it also in all debates of what kind soever. And when men that think themselves wiser than all others clamour and demand right reason for judge, yet seek no more but that things should be determined by no other mens reason but their own, it is as intolerable in the society of men as it is in play after trump is turned, to use for trump on every occasion that suit whereof they have most in their hand. For they do nothing else that will have every of their passions, as it comes to bear sway in them, to be taken for right reason, and that in their own controversies, bewraying their want of right reason, by the claim they lay to it.

The use and end of reason is not the finding of the sum and truth of one or a few consequences remote from the first definitions and settled significations of names, but to begin at these, and proceed from one consequence to another. For there can be no certainty of the last conclusion without a certainty of all those affirmations and negations on which it was grounded and inferred. As when a master of a family in taking an account casteth up the sums of all the bills of expense into one sum, and, not regarding how each bill is summed up by those that give them in account nor what it is he pays for, he advantages himself no more than if he allowed the account in gross, trusting to every of the accountants skill and honesty; so also, in reasoning of all other things, he that takes up conclusions on the trust of authors and doth not fetch them from the first items in every reckoning, which are the significations of names settled by definitions, loses his labour, and does not know anything, but only believeth.

When a man reckons without the use of words, which may be done in particular things, as when upon the sight of any one thing we conjecture what was likely to have preceded or is likely to follow upon it, if that which he thought likely to follow follows not, or that which he thought likely to have preceded it hath not preceded it, this is called error, to which even the most prudent men are subject. But when we reason in words of general signification, and fall upon a general inference which is false, though it be commonly called error, it is indeed an absurdity, or senseless speech. For error is but a deception, in presuming that somewhat is past or to come, of which, though it were not past or not to come, yet there was no impossibility discoverable. But when we make a general assertion, unless it be a true one, the possibility of it is inconceivable. And words whereby we conceive nothing but the sound are those we call absurd, insignificant, and nonsense. And therefore if a man should talk to me of a round quadrangle, or accidents of bread in cheese, or immaterial substances, or of a free subject, a free will, or any free but free from being hindered by opposition, I should not say he were in an error, but that his words were without meaning, that is to say absurd.

I have said before, in the second chapter, that a man did excel all other animals in this faculty that when he conceived anything whatsoever he was apt to inquire the consequences of it, and what effects he could do with it. And now I add this other degree of the same excellence, that he can by words reduce the consequences he finds to general rules, called theorems, or aphorisms, that is, he can reason, or reckon, not only in number, but in all other things whereof one may be added unto, or subtracted from another.

But this privilege is allayed by another, and that is, by the privilege of absurdity; to which no living creature is subject, but man only. And of men, those are of all most subject to it that profess philosophy. For it is most true that Cicero saith of them somewhere that there can be nothing so absurd but may be found in the books of philosophers. And the reason is manifest. For there is not one of them that begins his ratiocination from the definitions or explications of the names they are to use, which is a method that hath been used only in geometry, whose conclusions have thereby been made indisputable.

I. The first cause of absurd conclusions I ascribe to the want of method, in that they begin not their ratiocination from definitions, that is, from settled significations of their words; as if they could cast account without knowing the value of the numeral words one, two, and three.

And whereas all bodies enter into account upon divers considerations, which I have mentioned in the precedent chapter, these considerations being diversely named, divers absurdities proceed from the confusion, and unfit connexion of their names into assertions. And therefore:

II. The second cause of absurd assertions I ascribe to the giving of names of bodies to accidents, or of accidents to bodies, as they do that say faith is infused or inspired, when nothing can be poured or breathed into anything but body; and that extension is body, that phantasms are spirits, etc.

III. The third I ascribe to the giving of the names of the accidents of bodies without us to the accidents of our own bodies, as they do that say the colour is in the body, and the sound is in the air, etc.

VI. The sixth to the use of metaphors, tropes, and other rhetorical figures, instead of words proper. For though it be lawful to say, for example, in common speech, the way goeth, or leadeth hither or thither, the proverb says this or that, whereas ways cannot go, nor proverbs speak; yet in reckoning and seeking of truth such speeches are not to be admitted.

VII. The seventh to names that signify nothing, but are taken up and learned by rote from the schools, as hypostatical, transubstantiate, consubstantiate, eternal-now, and the like canting of schoolmen.

To him that can avoid these things it is not easy to fall into any absurdity, unless it be by the length of an account, wherein he may perhaps forget what went before. For all men by nature reason alike, and well, when they have good principles. For who is so stupid as both to mistake in geometry and also to persist in it, when another detects his error to him?

By this it appears that reason is not, as sense and memory, born with us, nor gotten by experience only, as prudence is; but attained by industry, first in apt imposing of names, and secondly by getting a good and orderly method in proceeding from the elements, which are names, to assertions made by connection of one of them to another, and so to syllogisms, which are the connections of one assertion to another, till we come to a knowledge of all the consequences of names appertaining to the subject in hand; and that is it men call science. And where as sense and memory are but knowledge of fact, which is a thing past and irrevocable, science is the knowledge of consequences, and dependence of one fact upon another, by which, out of that we can presently do, we know how to do something else when we will, or the like another time; because when we see how anything comes about, upon what causes, and by what manner, when the like causes come into our power, we see how to make it produce the like effects.

Children therefore are not endued with reason at all, till they have attained the use of speech; but are called reasonable creatures, for the possibility apparent of having the use of reason in time to come. And the most part of men, though they have the use of reasoning a little way, as in numbering to some degree, yet it serves them to little use in common life, in which they govern themselves, some better, some worse according to their differences of experience, quickness of memory and inclinations to several ends; but specially according to good or evil fortune, and the errors of one another. For as for science, or certain rules of their actions, they are so far from it that they know not what it is. Geometry they have thought conjuring; but for other sciences, they who have not been taught the beginnings and some progress in them, that they may see how they be acquired and generated, are in this point like children that, having no thought of generation, are made believe by the women that their brothers and sisters are not born but found in the garden.

But yet they have no science are in better and nobler condition, with their natural prudence, than men, that by mis-reasoning, or by trusting them that reason wrong, fall upon false and absurd general rules. For ignorance of causes and of rules does not set men so far out of their way as relying on false rules, and taking for causes of what they aspire to those that are not so, but rather causes of the contrary.

To conclude, the light of human minds, is perspicuous words, but by exact definitions first snuffed and purged from ambiguity; reason is the pace, increase of science the way, and the benefit of mankind the end. And, on the contrary, metaphors, and senseless and ambiguous words, are like ignes fatui; and reasoning upon them is wandering amongst innumerable absurdities; and their end contention and sedition, or contempt.

As much experience is prudence, so is much science sapience. For though we usually have one name of wisdom for them both, yet the Latins did always distinguish between prudentia and sapientia, ascribing the former to experience, the latter to science. But, to make their difference appear more clearly, let us suppose one man endued with an excellent natural use and dexterity in handling his arms, and another to have added to that dexterity an acquired science of where he can offend or be offended by his adversary in every possible posture or guard: the ability of the former would be to the ability of the latter as prudence to sapience, both useful, but the latter infallible. But they that, trusting only to the authority of books, follow the blind blindly are like him that, trusting to the false rules of a master of fence, ventures presumptuously upon an adversary that either kills or disgraces him.

The signs of science are, some certain and infallible, some, uncertain. Certain, when he that pretendeth the science of anything can teach the same, that is to say, demonstrate the truth thereof perspicuously to another; uncertain, when only some particular events answer to his pretence, and upon many occasions prove so as he says they must. Signs of prudence are all uncertain, because to observe by experience, and remember all circumstances that may alter the success, is impossible. But in any business whereof a man has not infallible science to proceed by, to forsake his own natural judgment, and be guided by general sentences read in authors and subject to many exceptions, is a sign of folly, and generally scorned by the name of pedantry. And even of those men themselves that in councils of the commonwealth love to show their reading of politics and history, very few do it in their domestic affairs, where their particular interest is concerned, having prudence enough for their private affairs; but in public they study more the reputation of their own wit than the success of anothers business.